We have literature indicating that overwhelmingly, health is influenced by a very short list of modifiable behaviors topped by three: tobacco use, physical activity and dietary pattern. You could modify those three things; you can change people's fate. I wanted to change those. Smoking cessation, important but relatively simple - a lot of people are working on that. Physical activity: important to me, important to health but also relatively simple. I like nutrition. It's complicated; you really need to learn a lot of stuff to be an expert there.